Sun protective clothing was originally popularized (but not exclusively used) in Australia as an option or adjunct to sunscreen lotions and sunblock creams. Sun protective clothing and UV protective fabrics in Australia now follow a lab-testing procedure regulated by a federal agency: ARPANSA. To date, the focus for sun protection is swimwear, appropriate hats, shade devices and sunglasses for children.

The original UPF rating system was enhanced in the United States by the ASTM (American Standards and Testing Methods) Committee D13:65 at the behest of the FDA (Food and Drug Administration) to qualify and standardize the emerging sun protective clothing and textile industry. The UPF rating system may eventually be adopted by interested apparel and domestic textile/fabric manufacturers in the industry at large as a "value added" program strategic to complement consumer safety and awareness.

Fabric

Factors that affect the level of sun protection provided by a fabric, in approximate order of importance, include weave, color, weight, stretch,  and wetness. In addition, UV absorbers may be added at various points in the manufacturing process to enhance UV protection levels.

There is some indication that washing fabrics in detergents containing fabric brighteners, which absorb UV radiation, might increase their protective capability. Studies at the University of Alberta also suggest that darker colored fabrics can offer more protection than lighter colored fabrics.

Summary UPF Testing Protocol

AATCC 183 method defines the UPF rating for a fabric/textile as the ratio of UV measured without the protection of the fabric (compared to) with protection of the fabric. For example, a fabric rated UPF 30 means that if 30 units of UV fall on the fabric only 1 unit will pass through. A UPF 30 fabric that blocks or absorbs 29 out of 30 units of UV is therefore blocking 96.7% UV. UPF tests are normally conducted in a laboratory with a spectrophotometer or a spectroradiometer.

AATCC 183 should be used in conjunction with other related standards including American Society for Testing and Materials (ASTM) D 6544 and ASTM D 6603. ASTM D 6544 specifies simulating the life cycle of a fabric so that a UPF test can be done at the end of a fabric's life cycle
which is when most fabrics provide the most reduced level of UV protection. ASTM D 6603 is a consumer format recommended for visible hangtag and care labelling of sun protective clothing and textiles. A manufacturer may publish a test result to a maximum of UPF 50+.

While there is some correlation between the amount of visible light that passes through a fabric and the amount of UV that passes the same fabric, it is not a strong relationship. Based on some of the new-technology fibers and textiles designed for the sole purpose of UV blocking, it is not always possible to gain a good understanding of the UV protection level of a fabric simply by holding it up and examining how much visible light passes through the fabric.

Sun protective clothing and textile/fabric manufacturers are currently a self-regulating industry in North America, prescribed by the AATCC and ASTM methods of testing.

External Links

• Learn more about sun-protective clothing from The Skin Cancer Foundation

References

Gies, H.P., Roy, C.R., Elliot, G., & Zongli, W. (1994). "Ultraviolet Radiation Protection Factors for Clothing". Health Physics 67 (2): 131-139. 

Gambichler, T., Rotterdam, Altmeyer, P., & Hoffmann, K. (2001). "Protection against ultraviolet radiation by commercial summer clothing: need for standardized testing and labelling.". BMC (BioMed Central) Dermatology I: 6-9. 

ARPANSA

American Association of Textile Chemists and Colorists (AATCC) Test Method 183

American Society for Testing and Materials (ASTM) Standard D 6544

American Society for Testing and Materials (ASTM) Standard D 6603

Stanford, Duncan G., Georgouras, Katherine E. & Pailthorpe, Michael T. (1997). "Rating clothing for sun protection: current status in Australia". Journal of the European Academy of Dermatology & Venereology 8 (1): 12-17.